Question

Here’s my data:

+----------+---------------+------------+---------------------+
|  doctor  | received_date | patient_id | accession_daily_key |
+----------+---------------+------------+---------------------+
|  A       |  1/1/2011     |  ABC123    |                   1 |
|  A       |  1/20/2011    |  AAA123    |                   2 |
|  A       |  1/21/2011    |  AAA123    |                   3 |
|          |               |            |                   4 |
|  A       |  2/1/2011     |  ABC123    |                   5 |
|  A       |  2/9/2011     |  BBBYYY    |                   6 |
|          |               |            |                   7 |
|  B       |  1/2/2011     |  ABC123    |                   8 |
|  B       |  1/20/2011    |  AXA435    |                   9 |
|  B       |  1/19/2011    |  AAA123    |                  10 |
|          |               |            |                  11 |
|  B       |  2/1/2011     |  ABC123    |                  12 |
|  B       |  2/10/2011    |  BBBYYY    |                  13 |
+----------+---------------+------------+---------------------+

Here’s the result I want:

+--------+-------+--------------------+
| doctor | month | count new patients |
+--------+-------+--------------------+
| A      |     1 |                  1 |
| A      |     2 |                  1 |
| B      |     1 |                  2 |
| B      |     2 |                  0 |
+--------+-------+--------------------+

I would like to count the new patients for a doctor every month.

The business rules I’ve been given are:

1. a patient can be associated with only one doctor
2. the doctor to which the patient is associated is the LAST doctor that saw him

Here’s what I have so far:

select patient_id,max(month(RECEIVED_DATE)) AS Mnth, max(year(RECEIVED_DATE)) AS Yr, ACCESSION_DAILY_KEY
    FROM [F_ACCESSION_DAILY] 
    where RECEIVED_MLIS_INFORMATION=1
    GROUP BY patient_id,ACCESSION_DAILY_KEY

This query will give me the primary key accession_daily_key of the row which contains the doctor to which the patient is associated with.

Can you please guide me on how I can get the number of patients every month that are NEW for each doctor in that specific month?

---

Edit by jcolebrand:

CREATE TABLE F_ACCESSION_DAILY (
    doctor VARCHAR(10) NOT NULL
  , received_date DATETIME NOT NULL
  , patient_id VARCHAR(10) NOT NULL
  , accession_daily_key INT NOT NULL
)

INSERT INTO F_ACCESSION_DAILY (doctor,received_date,patient_id,accession_daily_key) VALUES ('A','1/1/2011','ABC123','1')
INSERT INTO F_ACCESSION_DAILY (doctor,received_date,patient_id,accession_daily_key) VALUES ('A','1/20/2011','AAA123','2')
INSERT INTO F_ACCESSION_DAILY (doctor,received_date,patient_id,accession_daily_key) VALUES ('A','1/21/2011','AAA123','3')
INSERT INTO F_ACCESSION_DAILY (doctor,received_date,patient_id,accession_daily_key) VALUES ('A','2/1/2011','ABC123','5')
INSERT INTO F_ACCESSION_DAILY (doctor,received_date,patient_id,accession_daily_key) VALUES ('A','2/9/2011','BBBYYY','6')
INSERT INTO F_ACCESSION_DAILY (doctor,received_date,patient_id,accession_daily_key) VALUES ('B','1/2/2011','ABC123','8')
INSERT INTO F_ACCESSION_DAILY (doctor,received_date,patient_id,accession_daily_key) VALUES ('B','1/20/2011','AXA435','9')
INSERT INTO F_ACCESSION_DAILY (doctor,received_date,patient_id,accession_daily_key) VALUES ('B','1/19/2011','AAA123','10')
INSERT INTO F_ACCESSION_DAILY (doctor,received_date,patient_id,accession_daily_key) VALUES ('B','2/1/2011','ABC123','12')
INSERT INTO F_ACCESSION_DAILY (doctor,received_date,patient_id,accession_daily_key) VALUES ('B','2/10/2011','BBBYYY','13')

Answer 1

Note that this is on his first iteration of information, and because Zeb has already done a great job with a further answer, I’m leaving this for historical tracing reasons. Feel free to ignore this answer in favor of his, but for the iterative process, this is a good learning example.

This seems like it should do what you need, I think

SELECT
       MIN(received_date) AS FirstVisit
     , patient_id         AS PatientID
INTO #LookupTable
FROM F_ACCESSION_DAILY

SELECT 
       f.doctor           AS Doctor
     , COUNT(f.*)         AS CountNewPatients
     , MONTH(firstvisit)  AS Month
     , YEAR(firstvisit)   AS Year
FROM F_ACCESSION_DAILY f 
INNER JOIN #LookupTable l ON f.received_date = l.FirstVisit 
                         AND f.patient_id = l.PatientID
GROUP BY f.doctor
       , MONTH(firstvisit)
       , YEAR(firstvisit)

DROP TABLE #LookupTable